This application is for an automated x-ray diffraction system. The system would decrease the time of data acquisition and analysis and greatly enhance the accuracy of the results. Advances in high intensity x-ray tubes and slit systems will allow faster and more accurate analysis of diffraction patterns. The interactive computer system will result in more accurate qualitative and quantitative analyses. This multi-user facility will enhance the research of seven NIH investigators. Many materials studied by the users require x-ray diffraction for accurate and complete characterization. Differences in structure which can easily be detected by x-ray diffraction often are not revealed by other commonly used analytical techniques. This equipment will be used to study phase changes and corrosion products in dental amalgam restorations, dental cement reaction products, phase contents of investment materials, casting alloys, and porcelains, oxide bonding layers, phase contents and preferred orientation in implant alloys, and per cent crystallinity in medical polymers.